Bright plumage against green foliage: the grandeur and beauty of evolution
by Michael S. Webster | © Washington State University
"Art can be considered as a behavior . . . like play, like food sharing, like howling, that is, something humans do because it helps them to survive, and to survive better than they would without it." —Homo Aestheticus: Where Art Comes From and Why, Ellen Dissanayake '57
I open my hand and the little wren, momentarily startled by its newfound freedom, flutters quickly to the nearest bush. I stand in the hot tropical Australian sun and watch as the tiny bird flits from branch to branch, a black- and red-feathered jewel. I have just captured this little bird, collected a page full of data and a blood sample for genetic analysis back in the lab, and added some colored bands to his legs so that we can identify him later. The bird pecks quizzically at its leg bands and then lets forth a loud, twittering song. His mate responds quickly, singing her own song and then flying over to join him in the shrub. They hop around each other excitedly, and I smile as I watch them flit away and disappear into the eucalyptus forest.
I have come here from Pullman to the steamy edge of the Australian rainforest to study these little birds, known locally as "red-backed fairy-wrens." Working with my students and other collaborators, I am examining some of the mechanisms that help drive the evolutionary process. For years we have worked to understand how mating behavior can lead to the evolution of conspicuous traits, such as bright plumage and song, which are ubiquitous in the animal kingdom, yet puzzling, since they are likely to attract the attention of predators and so decrease survival. This puzzle is particularly vexing in birds such as fairy-wrens, which are socially monogamous and seem to show little if any competition for mates.
Our work has revealed a secret world among these little birds. Genetic analysis has shown that females often mate with males other than their social mates and that brightly colored males have a strong advantage in this hidden sexual competition. Thus, males who are more brightly colored sire more offspring, spreading more genes to the next generation, and coming out ahead in the game of natural selection.
But as in any good science, answering one question opens the door to a host of others. Why do females prefer brightly colored males? Why do some males nevertheless have drab coloration? And might this hidden reproductive competition be important somehow to the process of speciation-that is, the process by which a single species evolves to become two separate and distinct species? We are now expanding our research to address these questions, combining detailed observations of birds in the field, experimental manipulations of their family groups, and intensive genetic analyses in the laboratory. As bizarre (or humorous) as it may seem to my friends and family, I have devoted much of my professional career to understanding the sex lives of these funny little birds.
But why am I doing this? Why do I return to these tropical Australian forests each year to face-or at least ignore-the many snakes, insects, and horrifyingly large terrestrial leeches? What compels me to spend so much time delving into the breeding behavior and genetics of these little birds?
And I'm hardly alone. Why have so many other scientists, many here at Washington State University, devoted their careers to studying the genetics of snails and lizards, the evolutionary history of various plants, the development of beetle larvae, and a host of other such questions?
Part of the answer is that the research questions themselves are important. Evolutionary biology is a thriving discipline that involves thousands of scientists across the globe. Evolution is the unifying theme that puts the "why" into our understanding of biological systems. It tells us why organisms look and act and function the way that they do. It tells us why we have the diversity of life on earth that we have, and why so many species, like the dinosaurs, are no longer with us. And it tells us about our own family tree and where humans, as a species, came from. Indeed, as the evolutionary biologist Theodosius Dobzhansky put it several decades ago, "Nothing in biology makes sense if not in the light of evolution."
But, truth be told, that is only part of the answer, and none of that is what I am thinking about as I watch my little wrens flit away. Instead, I am thinking about how pretty they are, bright plumage against the green foliage, twittering songs bouncing off the leaves. This, of course, is why I am here and why I have devoted my career to studying behavior and evolution-I am fascinated with these little birds and want to understand as much as I can about them. This fascination is shared by the students working with me here in Australia. Around the dinner table at night we chat about the birds, what we saw them doing that day, and also any other interesting little tidbits we observed, like the large carpet python hunting through the brush this morning. To be sure, we also talk a lot about science-the data we are collecting and the ideas that we are testing-but a good deal of our time is spent just chatting about our many nonhuman neighbors in the forest that surrounds us.
This fascination with nature is what drives and compels evolutionary biologists. There is little fame in this line of work, and little fortune. Rather, what drives people into this line of work is equal parts innate curiosity and deep appreciation for nature. Evolutionary biologists-indeed most scientists in general-are obsessed with solving questions about nature. Some of these questions and puzzles are big ones, but for the most part they are small questions about tiny aspects of nature. The answers to these many little questions, though, add up to a larger understanding of nature and how it operates.
Charles Darwin, the original architect for the modern theory of evolution, himself typified this mixture of deep curiosity and love for nature. As a young man Darwin set out on a five-year voyage around the world, during which he occupied himself with observing, describing, and thinking about what he saw. His observations led to questions and puzzles. Why were so many fossil animals similar to, but slightly different from, living organisms in the same areas? Why did the depth of a flower so closely match the tongue length of its pollinator? Why did the birds on an island resemble each other in so many ways except size of the bill? These observations and questions led Darwin to formulate the Theory of Evolution by Natural Selection, and biologists to this day continue to uncover the details of that process. Throughout the rest of his career Darwin devoted himself to studying the flowering habits of orchids, the lives of mollusks, the effects of worms on mould, and the expression of emotion in animals. Throughout it all, he was driven always by that innate curiosity and love.
Some have told me that this evolutionary explanation robs nature of beauty by reducing it to a cold mechanical process, "red in tooth and claw," as the saying goes. This attitude puzzles me, because all the evolutionary biologists whom I know-and I know many!-are driven by a love for nature, and to them nothing is more exciting than to uncover some hidden aspect of a natural system. Darwin himself probably best described this fascination that evolutionary biologists have with the natural world when he wrote these closing lines to his first book on evolution, The Origin of Species: "There is grandeur in this view of life, . . . that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved."
Michael Webster is an associate professor in the School of Biological Sciences. His research focuses on the evolution of sexually elaborate traits, such as bright plumage, and reproductive behaviors in wild birds.
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